Transmission system regulation



Aug- 17, 1943. P. s. EDWARDS 2,326,770

TRANSMISSION SYSTEM REGULATION- Filed Sept. 9, 1941 2 Sheets-Sheet l l2 /f' l L1 l fn A B U l2 F/G. NMA r/VE 15m? oofrr/c/EA/r 0F REI/572ML' Q FIG. /8 ATTO/a V Aug. 17, 1943. P. G. EDWARDS TRANSMISSION SYSTEM REGULATION Filed Sept. 9, 1941 2 Sheets-Sheet 2 x-l-IlTIII- III,||I1.|I

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t' Patented Aug. `17, 1943 v frrltnNsr/nssroiv. SYSTEM REGULATION raul G; news1-fasi verona, itl.; assigo to Benfl Telephone Laboratories, Incorporated, (New, York, N. -Y.,.a corporation lci. NewYork. Y

Appia-alien september e, 1941,ssriaino-41a14e t f This invention relates to transmissionlines and more particularly to means for compensatingifor variations in transmission characteristics of i such lines due to variations intemperature. The arrangements of the invention areV particularlyr adapted for use on a-telephone line,` either of V.the open wire or cabletype.

tocompensate for variations' inv 1the characterise, tics of the 1transxnssior1 line withk variationsinY climatic 'or'atmospheric-1temperature; j-

Y I-orm typical'networks which, in accordance-With ,the

An ordinary telephone line hasapositive vari- Y ation of resistance with temperature overV the limited range embraced by atmospnerictemperatures.` In thelUnited States Patent 2,050;703,jto LLB. Johnson, August `1'1, 1936, thereis Vdi'scll'nseql a means for compensating :for Suche variationz Figs. 2,3 andV l illustrate in generalized invention, may 1,be employedffor 'Y compensation purposes, the network incorporating a single reactance component-,orelement;-

rigs; 2A, ,3A and 4A, illustrate'l VKspecies-j neta t 'Y worksfbased uponthose ofelies; l2, 3 and 2i;

Figs; 5 toi-15` illustrate additional networks-in Y generalized forni that may be,.employedf-imgace of resistance inzthe lineidue, tol-temperature changes. I This comprises inserting in the line a' compensating UlnitV comprising av Variable resistance having a `negative temperature :scenici-ent of resistance in parallel with a resistance having a small temperature coefficient.. By utilizing such Y havingassociated with it 'alcorn'bination of one"v or more other elements', one of which may be 'a reactance, having their constants so cliosenvwith respect to 'eeen other and the line'cthat theunit' wil coinpensate'for .both attenuation vchangesv and impedance changes in the `line: due totemperature changes Another'o'bject of theinvention is to compensate further for the impedance' changes in the line due to temperature'lclianges by utilizing a plurality vof compensating units spacesl at predetermined' points, or at denite in- Y tervals, in 'the line. -Gtherobjects and features of the invention will appearrmorefully from the detailed. description thereof hereinafter given,

A incre complete #understanding o thisinvention will be obtainedffr'om the ldetailed description which follows taken in .con-junction withV theA appended dra-wines, wherein: Y f

changes Vin tile-Iiifiefclne` totemperature f a compensating unit comprising. atem'f.' Y

' variation inthe temperature'of i-ts-.Isurroundings' cordanlce with -the invention; 'theY networks-off.' Vthese figures, however, incorporatingat y,leastjtworeactan'cecompo'nentsor elements; r v

Figs-'18 and 1-7. show' speciiic rif-twentev porating a plurality of rcpeatersorv ampliers at spaced-intervals in a transmissionline,'witli compensating networks inserted inV the1 lin-e in-l termediate the repeater points; 1

Fig. 19- illustrates a Jloaded transmission L Y' in which compensating networks are inserted at` the .2, .S Ypoints betweenloading-coils; .A

5Fl-g.- 2() illustrates a loaded' transmissionfline in which compensating networks are inserted at the midpoints A between the loading--coils and Figll lllustratesfa/loaed transmise ion:lineYy in which compensating :networks are insertedV atl thev loading coils-f With `particular -r extendingA betwenfgeographically Yseparated `re-v gions or points, and comprising a pairA of tele-'- phone conductorsorfwiresv H. `The line may-be of the, soecalled open-wire type, or may comprise one ofy a large number of telephon'epairs included'k in a suitable cable. Such 'a line will underg'oboth l attenuationfchanges and impedance changes with f variation rin its "temperature` as determined -by Y Inserted vin the line atpreassigned intervals and tions inits temperature.' The unit l2 maybe'of;` Vtile type disclosed in-J; B. Johnson Patent. Y

Fig. rrenresents a-transmission linefor.,path y comprising a pair of telephone conduct-oreal wires lhaving inserted therein 4means or networks preferably in each conductor of the line-for pur-y poses of symmetry, is a compensator vunit or net -f work-l2 to compensate in `'part or in :wholefor variations gin theV line. characteristics with Varia.-

2,050,703 of'Augnstr 11, 1936, but irl-accordance withv this invention, itgis preferred toen'iploy a molicationof such unit that includes'fone or more -reactance `components* or elements, 'Illaf-` line may be ofthe loadedl or of themen-loaded naar upon the generalized.networks` of Figs'-61and 13;-

Fig. 18 illustrates-atransmission system incor-r encelto Fig.V .1, therais Y shown :therein-*a ltransmissionjfpatfnor Jlineflk 2 I Y* s s f As shown in Figs. 2, 3 and ,4, the unit l2 may comprise a temperature-dependent resistance element orthermistor T, and a resistance Rs of small e temperature coefficient of resistance, for example, Y

VVas suggested in the beforementioned Johnson patent, together with a reactanceelement or component indicated by the :n inv each of Figs. 2, 3 and 4.

This reactance element may be either capacitive or inductive, and inthe arrangement of Fig. 2 is' shown as connected in parallelwith the resistance elements; in Fig. 3, it is shown aS connected.-

ance; and in Fig. 4, it is shown connected in seriesV with the resistance Rs.v Thereactance element is included in the network in order to'provide compensation for changes in the limpedance of vthe line with changes in temperature, and/or toY in series with the temperature-dependent resistv' regarding;

, (l) The line impedance at the point of insertion and the proper determination of such a point;

control the attenuation-temperature-frequencycharacteristic. Y x

Figs. 2A, 3A and 4A show compensating units ornetworks of the general type shown in Figs. 2, 3 and 4, respectively. The network or unitofv Fig. 2A is particularly adapted for insertioninY a loaded cable telephone pair1 over which voice frequency currents are to be transmitted.V In this unit,-arcapacitance C is connected in parallel with the temperature-dependent resistanceand the resistanceRs. The unit of Fig. 3A is adapted for use ina similar situation, but comprisesV an inductance L connected in series with the -temperature-' dependent resistance T. The network of Fig. 4A' is particularly'adapted'for insertion in the conductors of a non-loaded telephone pair-,"for example, includedV in 'a'cable over which carrier fre-v quency currents are'to be transmitted*v In the Y arrangement of Fig. 4A, an inductance L is connected inseries with the resistanceRs; With'respeci: to the networks of'Figs. 2A, and-3A, when they are included in the ltelephone pair in lthe manner indi-,cated in Fig. 1, 'they-.provide compensation for b'oth' attenuation 'and' impedance changes in the transmission line resulting from variations in the temperature of the' latter. A

A more exact compensation for the change in the attenuation-and impedance characteristics of the transmission `line .may be obtained if'two or more reactanc'e elements are added to the J ohn; son tyoe network. f A large numberof'conigurations `is available and some ofthe-se are indicated in Figsf through 15, inclusive. VEach, of'lthese pendent resistance T, a''resistance' Rsof small temperature coefficient of resistance, and two reactance'elements. the location of the latter being. indicated hv a: and being either .capacitive or inductive. Figs 16 and .17 showrtwof specific networks eachV of which'. incorporates a capacitive and .an inductive reactive element. Y'Inethefarrange'- ment ofFig. .16, thecacacitive element C1 is con#V nected in series withv the inductive-,element Li, the K series connection of. theseelements being in shunt ing `a transmissionrpath or line I0 having a plurality of Vrepeaters A. B. Geinserte'd therein at spaced intervals, the conductors of the line interl mediate the Yrepeater points containing compen- Cil '(2) The frequency range it is desired to cover;

(3) VThe number and kinds of circuit elements Y in the compensating unit. e

Consider vfirst, the compensation of the arrangement of the simple network of the parallel thermistor T and'resistance Rs in its relation to anon-loaded pair of telephone conductors.. For purposes of compensating attenuation, Y.the rcsistance change of a full sectionof line, say 10 to 20 miles long, could beV compensatedxby one such unit at or near the mid-dle of the section up to say '3000 cycles. The effect-,on the terminal impedances Yis negligible.` Above '3000 cycles, orV thereabouts, .it becomes necessary to consider the addition' o'f 'additional elements. Fig. 4A shows the inclusion of an inductive element in the compensating unit or network so that the compensation varies with frequency in such a way that it is effective up toabout 2O kilocycles or beyond, whileY the compensation andthe impedance at frequencies below 2000A cycles may remain substantially unaffected. Thus, the network of Fig. 4A may be considered. as an extension of the simpler two-element network to cover a wide frequency range. 'One reason forV such a reiinement is that, at higher frequencies, the inductanc'e of the non-loaded line becomes important in determining the attenuation, reducing it below what it would bewth zero line inductance. It then'becomes desirable to vary the compensation accordingly, and one wayfto do .this is the inclusion of a compensating element whichV varies with frequency. in a 'complementary fashion. The compensating Yarrangement Vcan be considered as being insertedin the line characteristic impedance. 'I'he insertionloss so caused would then vary with frequency both because .ofthe variation with frequency of the characteristic impedance and the variation with frequency of the compensating unit. It is evident'from this discussion, then, that the degree of matching of the compensation which is obtained is' determined by the number Y and ,kind of elements which are included in the compensating unit. While the matter has been discussed on a physical basis, as will the following't'reatments, any and all of the assertions can and have beend'emonstrated mathematically, as Well as applied in practice.

Consider now the effect on impedance in a non-loaded pair of telephone conductors. If the compensating unit, pure'resistance for example, is included'at the line terminals, it will add directly 'to the terminal impedance previously ob` tained. As the compensating unit is moved away fromithe terminal-its effect on the impedance will be less and less due to the masking effect of the intervening lineruntil, as noted above, at a distance of some 10 miles, its effect on the im f pcdance is Verysmall. .The effect on attenuation,

-of said.' cable .pair being variable with temper'- l ature, and means to compensate forv s uchvariations comprising an impedance network inserted vimpedance characteristics vary with temperature', and meansfor compensating for such variations comprising animpedance network inserted in said cable, said network comprising an element having a negative-temperature coeiii-v v cient ofresistance and a capacitance in shunt therewith.

5. A transmission line whose attenuation and impedance characteristics vary with temper-v ature, and means to compensate for such variations comprising an impedance network inserted in said linein series therewith, said network comprising a temperature-dependent resistance and an inductance element.

6.1 A transmission line'whose attenuation and impedance characteristics vary with' temperature, and meansto compensate for suchivariations comprisingan impedance network inserted in said line in series therewith, said network comprising a temperature-dependent resistance anda capacitance element.

'7; A transmission line whose attenuation and impedance characteristics vary with temperature, and means tofcompensate for such variationscomprising an impedance network inserted in said line, said network comprising a temperature-dependent resistance and a reactance elementin series shunted by a'resistance ofsmall temperature coeicient. i

8; A transmission line whose attenuation and impedance characteristics vary `with. temperature, and means'to compensate for vsuch Variations comprising an impedance network inserted in said line, said network comprising a temper-- ature-dependent resistance and an inductanceY to that 'of vfrequency,v andmeansfinserted in' :said line tocompensate forrsaid .tendencies whereby the attenuation remains substantially constant with temperature change and'for all of the frequencies thetransmitted band, said means comprising a ytemperature-dependent `resistance that changesin resistancein av direction opposite to that of the temperaturefand a reactance element that varies :with frequency complementaryto thatzof the line. i 1

13. `In combination, aloaded transmission line comprising VaV plurality of loading` sections, the attenuation of said line tending rto change in the same directionv as that of its'temperatureg'and means inserted in each loading section to-maintain the effective attenuation of-k said line substantially constant with temperature change, said means comprising a temperature-dependent resistance whoseresistance change is in the .oppositedi'rection to that of temperature'change, said means beinginserted at thatr pointin the loading section at" which .the resistance component of the liney impedance is substantially constantxand the reactance components` inthe two directions of theV line are conjugate.V

14. Isn-combination, Va loaded transmission line in lwhichan impedance network isincluded in `each loading section in series Vwith the line `to compensateffor attenuation .change inv said .line

Y inv which yan impedance network isV included 'at element in series shunted by a resistance of small I temperature coefficient.

9. A transmission line'whcse attenuation and impedance characteristics vary with temperature, 'and means to compensate for such variations comprising 'an impedancenetwork inserted in. said line in series therewith, Asaid network comprising va temperature-dependent resistance comprising a temperature-dependent resistance and a shunt around said resistance including an inductance element.Y f a 11.7A transmission line whose attenuation and impedance characteristics vary with tempereach loading coil lin series with the line to compensate for attenuation ichange in said'line with temperature change,said network Acomprising-a temperature-dependent resistance anda reactance element.A '5 i L l f Y Vv116. 'In combination,l a lloaded .telephone pair, the 'attenuation and impedance characteristics of said-telephone pair'beingvariable with temper- Vature, and: means tocompensate for such variation comprising an impedance network inserted in the telephone pair in series therewith, said network including an element having a'negativ'e temperature coelcient of resistance and being located'between successiverloading coils, spaced from one coilV approximately .8 of'rthe distance between the coils andfrom' the lother coil approximately2 of; the distance. between thecoils. 17. The combination-of ,claim .16 in which said network also includes aireactanoe element. 418; The combination of claim 16` in which said network also includes a reactance in series with said resistance element.

19. The combinationof'claim 16 in which said network ralso includes an inductance in series with said resistance element, and a resistance of low temperature coefficient connected in parallel with the series-connected negative'resistancev l element and inductanee n 4 ature, and means to compensate for such varial tions comprising an impedance network inserted Yin said line in series therewith,'said network comprising a temperature-dependent resistance and az shunt around Said resistance including a capacitance element.

20. The combination of a transmission line subjected to Avariable temperature whereby the attenuation and impedance characteristics ofthe line 'vary with temp'eratureandme'ans serially included in said'line 'and subjected to the same variableftemperature as said line tocompensate for the effect of such temperature variations on said characteristics, said means comprising an `impedance network including an element having a temperature coeiicient oiresistance opposite to that of the line whereby resistance changes in said line and said element in response to temperature variations thereof :tend to; compensate one another, and a reactance'element to com-zV pensate for the effect on the attenuation of the line of the inductance of the line with increasing frequency.

21. A transmission line Whose attenua ion and Y impedance characteristics Vary with temperature and which is subjected to a variable temperature,

and means to compensaterfor Such variations` in said characteristic 'comprisingn an impedance network inserted in said line in series therewith and subjected to the same variabletemperature,

273. The combination of claim 21 in which said transmission line Ycomprises 'a loadedtelephone v which voice frequency currents are to be pair over transmitted and in which `the reactance element of the kimpedance network comprises an in-rV I ductance in series with the terrncerature-dependent resistance.

24. VThe combination of claim 21 in machine" Ar temperaturedependent resistance .and the reactance element of the impedance-network are connected in series, the series connection being shunted by a resistance of small temperature coefficient. Y

25. The mbmauon' of claim 21 in which-th reactance elenfientv of -the impedance .networkv comprises an inductance 'connected in series with the resistance,v the v, series yconnection 'being shunted byv a resistance cf small temperature lc'o-y eicient. Y Y

PAUL G. EDWARDS. 

